element library {
  element book {
    attribute id { text },
    attribute available { text },
    element isbn { text },
    element title {
      attribute xml:lang { text },
      text
    },
    element author {
      attribute id { text },
      element name { text },
      element born { text }?,
      element died { text }?
    }+,
    element character {
      attribute id { text },
      element name { text },
      element born { text }?,
      element qualification { text }
    }*
  }+
}
